Scanners are important devices in information processing. For example, by using a scanner, the contents of a book can be transferred to digital image data saved in a computer. Further, the digital data can be compressed and saved in a hard disk with smaller memory space and the digital data can be delivered to a remote location through networks or a fax machine.
It is a line-by-line process to scan documents with a scanner. For example, the scanned image of a document is composed of all line information. Hence, the resolution of a scanner is determined by the number of the scanning device's pixels per unit length. The major scanning devices of a scanner are a lens and a charge coupled device (CCD). The captured image of a document is projected by the lens onto the CCD. If there is no scan-range-changing mechanism in the scanner, it will happen that the whole image of a document with larger size cannot be completely scanned, and the resolution of scanned images is not adjustable. This kind of scanners is not user friendly.
Taiwan Pat. No. 235,112 describes a multi-lens scanner, which is composed of a sensor's seat and a lens device. The sensor's seat is set at an appropriate location, and the lens device locates ahead the sensor's seat. The lens device is bar-shaped with suitable length, and, upon it, these are a plurality of lenses for scanning, which these are equally spaced. On the bottom of the lens device, there are a curved groove and a rack fixed near one end of the curved groove. Under the lens device, there is a base, where a curved guide is fixed on the base's top at a location related to the curved groove, and the curved guide slides in the curved groove. In addition, there is a set of pinions engaged with the rack. The set of pinions can be clockwise or counterclockwise driven by a motor, and the rack is then moved. Consequently, the lens device is moved on the base.
It is important that, in the prior art, there is no mechanism to support the alignment of the sensor (such as CCD) and the lens. Hence, there exist the following drawbacks:
1. Misalignment and misfocus of the sensor and the lens can easily happen when the scanner is delivered. PA0 2. The compatibility of the scanner is poor. If there are multiple lenses with different focus lengths, a blurry image of a document is generated when the lens is changed to another. The scanning quality is consequently reduced.